Catalyst for hydrotreating

ABSTRACT

The invention provides a titania-zirconia or a titania-zirconia-alumina catalyst base containing a system of metals, metal oxides or metal sulfides from Groups VIB and VIII of the Periodic Table. Such catalysts are useful in the hydrodesulfurization and denitrogenation of hydrocarbon feed stocks and the saturation of aromatics contained therein.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of application Ser. No. 642,957, filedDec. 22, 1975, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is concerned with hydrocarbon desulfurization,denitrogenation and aromatics saturation and a catalyst therefor. Moreparticularly, the invention is concerned with a metal, metal oxideand/or sulfide supported on a base of titania-zirconia or oftitania-zirconia-alumina.

2. Discussion of the Prior Art

It is well known that many petroleum stocks contain sulfur and nitrogen.It is desirable for many applications of the petroleum stock itself orof the products made from it that these be removed. This is an operationrequiring a catalyst, and one in common use is an alumina basecontaining cobaltia and molybdena.

So far as is known, no art discloses catalysts or catalyst supports madeexclusively from titania-zirconia or titania-zirconia-alumina, or theuse of such supports containing cobaltia and molybdena or other metaloxides or sulfides in hydrotreating reactions. U.S. Pat. No. 3,159,588does disclose a catalyst containing various combinations of titania andzirconia, but it is essential to the composition that silica be presenttherein. There is no disclosure in U.S. Pat. No. 3,159,588 of thepresence of molybdena or cobaltia. U.S. Pat. Nos. 2,597,880, 3,137,658and 3,887,494 teach compositions of silica-titania, some containingother metals, in hydrocarbon conversion reactions. U.S. Pat. No.3,264,227 teaches the manufacture of a silica-zirconia-alumina catalystuseful in hydrocarbon conversion reactions.

U.S. Pat. No. 3,278,421 is concerned with refractory inorganic oxidescomprising alumina, titania and zirconia, among others, which maycontain certain metallic components. There is, however, no disclosure ofthe particular catalysts of the present invention.

U.S. Pat. No. 3,546,103 teaches hydrodesulfurization with a catalyst ofcobalt and molybdenum on an alumina base.

Some of the above-mentioned compositions of the prior art, as forexample the silica-titania-zirconia composition, allegedly havedesulfurization capabilities. However, the prior art mentioned does notteach or suggest the catalyst of this invention or its use inhydrotreating feed stocks.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided ahydrotreating catalyst composition consisting essentially ofco-precipitated titania and zirconia, subsequently used as a base forthe impregnation of a system selected from (a) the metal oxides orsulfides of Group VIB, (b) the metals, metal oxides and metal sulfidesof Group VIII and (c) mixtures thereof. Such mixtures include mixturesbetween Groups VIB and VIII and from within Group VIII. Preferredamounts of each range from about 20% to about 80% of titania, from about80% to about 20% of zirconia, from about 1% to about 10% of the GroupVIII metal, oxide or sulfide and from about 2% to about 20% of the GroupVIB oxide or sulfide. The amounts of metal, oxide or sulfide componentsare given in percent by weight of the carrier on a dry basis.

Provided also is a hydrotreating catalyst composition consistingessentially of co-precipitated titania and zirconia, composited withalumina, or of co-precipitated titania, zirconia and alumina,subsequently used as a base for the impregnation of a system from GroupVIII of the Periodic Table, its oxides or sulfides and from the metaloxides or sulfides of Group VIB. Preferred amounts of each will be fromabout 10% to about 50% of alumina, from about 15% to about 45% oftitania and from about 25% to about 65% of zirconia. Preferred amountsof metals, metal sulfides and oxides in the catalyst will be from about2% to about 10% of the Group VIII metal, oxide or sulfide and from about5% to about 20% of the Group VIB metal oxide or metal sulfide. Theamounts of metal, oxide or sulfide components are given in percent byweight of the carrier on a dry basis. The invention also provides amethod of hydrotreating using the catalysts.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The hydrotreating conditions employed herein involve passing thehydrocarbons over the finished catalyst at temperatures ranging betweenabout 300° F. and 1200° F. preferably between 600° F. and 1000° F.,hydrogen pressures above about 100 psig, preferably between about 250and 2500 psig, and space velocities ranging between about 0.25 and 10.The preferred hydrogen ratios may range between about 500 and 10,000 scfper barrel of feed.

The catalysts of this invention are useful for removing nitrogen, metalsand sulfur from such base stocks as naphthas, kerosene or range oil,fuel oils, including jet fuels, furnace oil, heavy gas oil and residuaand in saturating aromatics found in these stocks.

With respect to the catalysts made using the TiO₂ :ZrO₂ base, thecompositions found to be most useful for hydrotreating consistessentially of those which contain between about 20% and 80% ofzirconia, and between about 80% and 20% of titania, the proportionsbeing by weight on a dry basis, from about 1% to about 10% of thecarrier of cobaltia and from about 2% to about 20% of the carrier ofmolybdena.

The mole ratio of ZrO₂ to TiO₂ is preferably from about 0.5 to about2.0, with the optimum proportion of ingredients (i.e., ZrO₂ and TiO₂)being approximately equimolar. It has been found that this range ofconcentrations will also give the optimum surface area requirement,which is between about 100 m² /g and about 250 m² /g. As one increasesthe amount of one component relative to the other, the surface areaincreases to the value which yields the most useful catalyst (usually atequimolar amounts); as the concentration continues to increase thesurface area begins to diminish and will eventually fall below theminimum 100 m² /g. In other words, the surface area will decrease oneither side of the equimolar point to that of the pure component.

The compositions made using the TiO₂ :ZrO₂ :Al₂ O₃ base consistessentially of those which contain from about 10% to about 50% ofalumina, from about 25% to about 65% of zirconia, and from about 15% toabout 45% of titania, the proportions being by weight of the carrier ona dry basis, and from about 2% to about 10% of the carrier of cobaltiaand from about 5% to about 20% of the carrier of molybdena.

In the preparation of the titania-zirconia supports of this invention,it is essential that the components be extremely intimately mixed, suchas is achieved by co-precipitating of TiO₂ and ZrO₂. This support maythen be composited with Al₂ O₃, the necessary, or all components may bemixed to give the base TiO₂ :ZrO₂ :Al₂ O₃. Such supports may be preparedby any method which provides an intimate association of the components.Molecular subdivision and distribution of the components in anamorphous, activated gel structure is preferred.

One method of effecting the mentioned co-precipitation involves formingan aqueous solution of acidic compounds of the components, e.g. zirconylchloride, and titanium tetrachloride, and mixing this solution with asuitable alkali such as ammonium hydroxide, thereby to effect aprecipitation of the hydrous oxides of titania and zirconia. Theprecipitate is then removed by filtration, washed exhaustively to removecontaminating ions, dried and calcined.

Any suitable soluble salts or hydrosols of zirconium and titanium may beemployed. The objective is to obtain a mixture of the hydrous oxides, orof insoluble compounds which may be transformed to the oxides uponcalcining. Reactants include the titanium and zirconium halides, such aszirconyl chloride, bromide and iodide, titanium tetrachloride, -bromideand -iodide and other salts such as zirconium sulfate and titaniumoxalate.

The co-precipitated gels prepared by any of the mentioned methods arerecovered, as by filtration or the like, washed exhaustively, dried andcalcined at e.g. 1000° F. for 1 to 24 hours to form the oxide mixture.

In those catalysts containing alumina, alumina and water are added tothe calcined powder and the mixture is dried.

As is evident from the foregoing disclosure, the catalyst must containat least two components from the specified Groups. Preferably at leastone of the specified components (i.e., metal, metal oxide or metalsulfide) will be selected from Group VIII, e.g., Co, Fe, Ni, Pt and Pd.Another may be selected from Group VIB, e.g., the oxide or sulfide of W,Mo or Cr. These can be associated with the TiO₂ :ZrO₂ or the TiO₂ :ZrO₂:Al₂ O₃ carrier by any method known to the art. For example, they may beimpregnated, as was done in the practice of this invention. When this isdone, the metals (or their oxides or sulfides) can be added at once andcalcined, or they can be added separately, calcining following eachaddition. They are most usually and preferably added in the form ofaqueous solutions of their salts. The salts are selected so that theydecompose to the oxide upon calcination, e.g., nitrates.

Co-precipitated TiO₂ :ZrO₂ per se is an amorphous composition having arelatively high surface area. It is known to exhibit remarkable acidicproperties and to have catalytic activity [Acidic Properties of BinaryMetal Oxides, Shibata et al., Bull. Chem. Soc, Japan, Vol. 46, pp2985-2988 (1973). Also J. Res. Inst. Catalystis, Hokkaido Univ, Vol. 19,No. 1, pp 35-41 (1971)]. The latter reference teaches that theco-precipitated mixture remains amorphous even after calcination at 932°F.

Having described the invention in general terms, the following willspecifically illustrate its practice. It will be understood they areillustrations only and are not to be considered as limiting itunnecessarily.

EXAMPLE 1 Preparation of the Catalyst Comprising the Titania-ZirconiaBase

The titania-zirconia support was made by reacting a 50--50 mole %mixture of zirconyl chloride and titanium tetra-chloride with ammoniumhydroxide followed by washing, drying at 212° F. and calcination at1000° F. A 10 weight % molybdena content and a 3 weight % cobaltiacontent were obtained by first impregnating the initial calcined supportwith aqueous ammonium molybdate, treating with the minimum volume ofwater to dissolve the salt and wet the base, drying at 212° F. andcalcining at 1000° F., followed by a separate impregnation withcobaltous nitrate, followed by another calcination. The catalyst wasfound to have a surface area of 179 m² /gm and an average pore diameterof 80-100 A. Other details are disclosed in the above-noted Japanesearticle.

EXAMPLE 2 Preparation of Catalyst Comprising theTitania-Zirconia-Alumina Base

A combination of 18.33 g of TiCl₄, (0.167 mole TiO₂), 41.73 g of ZrOCl₂. XH₂ O (0.167 moles ZrO₂) and 80.48 g of AlCl₃ (0.167 mole Al₂ O₃) wasswirled in 6 liters of distilled water. The mixture was brought to a pHof 9-10. It was then filtered, washed by dispersing in 6 liters ofwater, filtered and re-dispersed in 6 liters of water. This mixture wasbrought to a pH of about 9 with NH₄ OH, stirred for 15 minutes andallowed to stand overnight. The mixture was filtered, dried at 230° F.and calcined for 2 hours at 1000° F.

To 10.0 g of the TiO₂ --ZrO₂ --Al₂ O₃ base prepared as above was added1.35 g of molybdic acid dissolved in 0.95 ml of concentrated ammoniumhydroxide in about 3.0 ml of water. The acid and ammonium hydroxidesolution were added, with mixing, to the solid until all particles wereuniformly wet. The mass was then dried at 230° F., followed by calciningfor 2 hours at 1000° F. It was cooled to room temperature andimpregnated with cobalt (as Co(NO₃)₂ ·6H₂ O).

This was done by dissolving 1.34 g of Co(NO₃)₂ ·6H₂ O in 3 ml of water,diluting to 4.0 ml and adding the solution to the molybdenum-impregnatedbase until all dry particles were wet. It was then dried at 230° F. andcalcined for 2 hours at 1000° F.

Evaluation of the TiO₂ -ZrO₂ Based Catalyst

A Kuwait residuum oil (see Column 1, Table 1) was passed over thecatalyst under the following conditions:

    ______________________________________                                        Temperature       775° F                                               Pressure          1000 psig                                                   Hydrogen          10,000 SCF/bbl                                              Space Velocity    1.0                                                         Catalyst          25 cc presulfided                                                             with H.sub.2 S                                              ______________________________________                                    

Table 1 summarizes the data.

Evaluation of the TiO₂ --ZrO₂ --Al₂ O₃ Based Catalyst

0.3 cc, 0.30 g, of CoMo TiO₂ --ZrO₂ --Al₂ O₃, containing 10% Mo and 3%Co was used in thiophene desulfurization runs. The catalyst waspretreated with H₂ S prior to use.

The thiophene was desulfurized under conditions as follows:

    ______________________________________                                         A                  B                                                         ______________________________________                                        400 psig           400 psig                                                   650° F      700° F                                              H.sub.2 /HC = 20/1 H.sub.2 /HC = 20/1                                         N.sub.2 rate = 533.6 cc/min                                                                      H.sub.2 rate =                                                                533.6 cc/min                                               Thiophene Charge rate =                                                                          Thiophene Charge                                           5.143 cc/hr (LHSV = 17.1)                                                                        rate = 5.143 cc/hr                                                            (LHSV = 17.1)                                              ______________________________________                                    

As compared to the commercial catalyst made with 9% Mo and 3% Co onalumina, which by definition here is 100%, activity (relative rateconstant), the catalyst used under conditions set out in A and Bdesulfurized thiophene to the extent of 74% and 58% relative activityrespectively, on a per unit volume basis.

                                      TABLE 1                                     __________________________________________________________________________    KUWAIT RESIDUUM OVER CoO . MoO.sub.3 /TiO.sub.2 . ZrO.sub.2                   __________________________________________________________________________    Period        1  A   B   C   D   E   F   G   H   I                            __________________________________________________________________________    Mid-period TOS (hrs.)                                                                       -- 2.9 14.0                                                                              26.0                                                                              38.0                                                                              49.8                                                                              61.8                                                                              73.8                                                                              85.8                                                                              96.2                         Period Length (hrs.)                                                                        -- 5.75                                                                              16.5                                                                              7.5 16.5                                                                              7.0 17.0                                                                              7.0 17.0                                                                              4.0                          Liquid Properties                                                             Gravity, ° API                                                                       18.4                                                                             29.8                                                                              25.7                                                                              23.8                                                                              22.8                                                                              22.8                                                                              22.9                                                                              23.0                                                                              23.0                                                                              22.9                         Sulfur, wt. % 3.92                                                                             0.377                                                                             0.982                                                                             1.473                                                                             1.681                                                                             1.752                                                                             1.708                                                                             1.770                                                                             1.870                                                                             1.871                        Nitrogen, wt. %                                                                             0.19                                                                             0.05                                                                              0.13                                                                              0.16                                                                              0.17                                                                              0.17                                                                              0.17                                                                              0.17                                                                              0.17                                                                              0.17                         Carbon, wt. % 84.5                                                                             --  86.88                                                                             86.66                                                                             85.87                                                                             86.23                                                                             85.94                                                                             85.94                                                                             86.45                                                                             85.81                        Hydrogen, wt. %                                                                             11.4                                                                             --  12.11                                                                             12.00                                                                             11.80                                                                             11.77                                                                             11.89                                                                             11.90                                                                             11.83                                                                             11.29                        Desulfurization, %                                                                          -- 90.5                                                                              75.1                                                                              62.7                                                                              57.4                                                                              55.6                                                                              56.8                                                                              55.2                                                                              52.7                                                                              52.6                         Denitrogenation, %                                                                          -- 73.7                                                                              31.6                                                                              15.8                                                                              10.5                                                                              10.5                                                                              10.5                                                                              10.5                                                                              10.5                                                                              10.5                         H.sub.2 Consumption,SCF/bbl                                                                 -- --  477 419 254 244 347 367 289 --                           Liquid Yield, wt. %                                                                         -- --  89.6                                                                              94.9                                                                              95.4                                                                              97.4                                                                              95.0                                                                              98.4                                                                              95.3                                                                              99.5                         Mass Balance, wt. %                                                                         -- --  93.4                                                                              98.3                                                                              98.0                                                                              100.6                                                                             98.2                                                                              102.4                                                                             98.7                                                                              --                           Period        J  K   L   M   N   O   P   Q                                    __________________________________________________________________________    Mid-period TOS (hrs.)                                                                       100.2                                                                            111.0                                                                             123.0                                                                             135.0                                                                             147.0                                                                             159.0                                                                             171.0                                                                             183.0                                Period Length (hrs.)                                                                        4.0                                                                              17.5                                                                              6.5 17.5                                                                              6.5 17.5                                                                              6.5 17.5                                 Liquid Properties                                                             Gravity, ° API                                                                       22.0                                                                             23.0                                                                              22.9                                                                              23.2                                                                              23.0                                                                              23.2                                                                              23.0                                                                              23.2                                 Sulfur, wt. % 1.89                                                                             2.014                                                                             1.972                                                                             1.980                                                                             2.014                                                                             2.016                                                                             1.970                                                                             1.972                                Nitrogen, wt. %                                                                             0.17                                                                             0.17                                                                              0.16                                                                              0.17                                                                              0.17                                                                              0.16                                                                              0.17                                                                              0.17                                 Carbon, wt. % -- 85.91                                                                             85.91                                                                             86.05                                                                             85.53                                                                             85.70                                                                             85.68                                                                             86.01                                Hydrogen, wt. %                                                                             -- 11.77                                                                             11.79                                                                             11.80                                                                             11.67                                                                             11.67                                                                             11.78                                                                             11.86                                Desulfurization, %                                                                          51.8                                                                             48.6                                                                              49.7                                                                              49.5                                                                              48.6                                                                              48.6                                                                              49.7                                                                              49.7                                 Denitrogenation, %                                                                          10.5                                                                             10.5                                                                              15.8                                                                              10.5                                                                              10.5                                                                              15.8                                                                              10.5                                                                              10.5                                 H.sub.2 Consumption,SCF/bbl                                                                 -- 230 249 262 186 176 268 311                                  Liquid Yield, wt. %                                                                         -- 95.0                                                                              92.3                                                                              98.6                                                                              95.0                                                                              97.6                                                                              94.2                                                                              97.8                                 Mass Balance, wt. %                                                                         -- 96.7                                                                              94.5                                                                              101.2                                                                             97.6                                                                              100.2                                                                             97.4                                                                              99.9                                 __________________________________________________________________________

CONVERSION WITH COMMERCIAL DESULFURIZATION CATALYST

Under the same conditions using a catalyst composed of 9 weight %molybdena and 3% cobaltia on alumina and the same feed stock, theresults shown in Table 2 were obtained.

                                      TABLE 2                                     __________________________________________________________________________    Period             A   B   C   D   E   F   G   H   I   J                      __________________________________________________________________________    Time Interval (hours)                                                                            0-3 3-6 6-22                                                                              22-30                                                                             30-46                                                                             46-54                                                                             54-70                                                                             70-78                                                                             78-95                                                                             95-98                  Mid-Period TOS (hrs.)                                                                            1.5 4.5 14  26  38  50  62  74  86.5                                                                              96.5                   Period Length (hrs.)                                                                             3   3   16  8   16  8   16  8   17  3                      Liquid Properties                                                                            Feed                                                           Gravity, ° API                                                                        18.4                                                                              30.7                                                                              27.0                                                                              25.7                                                                              25.0                                                                              24.7                                                                              24.5                                                                              24.2                                                                              24.1                                                                              24.0                                                                              23.8                   Sulfur, wt. %  3.89                                                                              .068                                                                              .27 .59 .80 .94 1.08                                                                              1.18                                                                              1.29                                                                              1.36                                                                              1.44                   Nitrogen, wt. %                                                                              0.19                                                                              .041                                                                              .10 .14 .16 .16 .17 .17 .17 .17 .17                    Carbon, wt. %  84.75                                                                             86.1                                                                              87.5                                                                              86.7                                                                              86.4                                                                              86.2                                                                              86.4                                                                              86.0                                                                              86.7                                                                              85.5                       Hydrogen, wt. %                                                                              11.4                                                                              11.7                                                                              12.5                                                                              12.3                                                                              12.2                                                                              12.2                                                                              12.2                                                                              12.1                                                                              12.2                                                                              12.1                                                                              12.2                   Ni, ppm        12  0.2 0.5 2.7 3.9 4.2 4.6 5.3 5.6 6.0 6.2                    V, ppm         46  0.1 0.3 2.2 3.9 5.5 7.2 8.9 9.5 10.0                                                                              10.0                   Desulfurization, %                                                                           --  98.3                                                                              93.1                                                                              84.8                                                                              79.4                                                                              75.8                                                                              72.2                                                                              69.7                                                                              66.8                                                                              65.0                                                                              63.0                   Denitrogenation, %                                                                           --  78.4                                                                              47.4                                                                              26.3                                                                              15.8                                                                              15.8                                                                              10.5                                                                              10.5                                                                              10.5                                                                              10.5                                                                              10.5                   % Ni Removal   --  98.3                                                                              95.8                                                                              77.5                                                                              67.5                                                                              65.0                                                                              61.7                                                                              55.8                                                                              53.3                                                                              50.0                                                                              48.3                   % V Removal    --  99.8                                                                              99.3                                                                              95.2                                                                              93.3                                                                              88.0                                                                              84.3                                                                              80.7                                                                              79.3                                                                              78.3                                                                              78.3                   H.sub.2 Consumption,                                                          (SCF/Bbl)      --  193 676 582 504 516 528 450 529 464 514                    __________________________________________________________________________     Time Avg. Hydrogen Consumption (SCF/BBL) from 50 to 96.5 hours (mid-perio     TOS) = 482                                                               

From the comparison shown it can be seen that after about 50 hours onstream, the catalyst of this invention showed little or no aging at50-54% desulfurization. The alumina based catalyst, however, althoughslightly more active, exhibited significant aging at comparable times onstream. Furthermore, the data show that the titania-zirconia catalyzedmaterial consumed approximately 27% less hydrogen for a given degree ofsulfur removal over times in excess of 50 hours.

Respecting the decrease in hydrogen consumption, it is believed this isreflected most clearly in a comparison of the liquid product in the twocases. As Table 1 shows, the titania-zirconia based catalyst gave aliquid product containing about 11.8 weight percent of hydrogen. Table2, on the other hand, shows a liquid product containing about 12.2weight percent of hydrogen, indicating higher hydrogen consumption forthe alumina-based catalyst. The oil used in obtaining the data in Table2 was the same as shown in Column 1 of Table 1.

Both the TiO₂ --ZrO₂ and the Al₂ O₃ -based catalysts reached a steadystate after about 50 hours, so the comparison mentioned above anddiscussed in detail below was made using data obtained on samples thathad been on stream greater than 50 hours. The comparison below was madeon the basis of time averaging so the catalysts could be compared at agiven level of catalytic performance, e.g., at the same level ofdesulfurization.

The table below sets forth data calculated from Tables 1 and 2.

    ______________________________________                                                   Time-Averaged                                                                            Time-Averaged                                                      % Desulfur-                                                                              H.sub.2 Consumption,                                               ization    SCF/BBL                                                 ______________________________________                                        TiZr-Catalyst                                                                 > 50 hours,                                                                   TOS, Periods                                                                  E-H and K-Q     51.2         268                                              Al.sub.2 O.sub.3 -Catalyst                                                    > 50 hours,                                                                   TOS, Period F-J 67.7         482                                              ______________________________________                                    

Time-averaged % desulfurization is calculated by multiplying each periodlength by the percentage desulfurization in that period, obtaining anoverall total and dividing that sum by the sum of the period lengths inall periods used. For example, the 51.2% above is obtained bymultiplying 7 (period length for period E in Table 1) by 55.6 (%desulfurization, period E) and so forth through the specified periods,adding to obtain 7250, then dividing by 141.5 (sum of appropriate periodlengths).

In a similar manner, the value 67.7 can be calculated from theappropriate data in the various periods. Values for hydrogen consumptionare calculated in the same way, using the appropriate period and thefigure for hydrogen consumption instead of % desulfurization.

It is known that a direct proportionality exists between hydrogenconsumption and the level of desulfurization [Buether, H., and Schmid,B. K., Section III, paper 20, Sixth World Petroleum Congress, June 19,1963, Frankfort/Main. Arey, W. F., Blackwell, N. E., III, and Reichle,A. D., Seventh World Petroleum Congress, 41167 (1967)]. Therefore, thedata can be adjusted to the same degree of desulfurization. Thus, for67.7% desulfurization, the titania-zirconia based catalyst wouldconsume:

    67.7 × 268/51.2 = 354 SCF/BBL

therefore, at the same desulfurization level, the titania-zirconia-basedcatalyst consumes 26.6% less hydrogen than the conventional aluminabased catalyst.

It can also be shown by a similar calculation that, if the whole run isused as a basis in both catalyst systems, the titania-zirconia systemstill consumes about 23% less hydrogen for a given desulfurization levelthat the alumina based system.

It should be emphasized that the nature of the comparison for a givencatalytic performance makes small differences in catalyst compositionincidental. The time-averaging calculation, in addition, tends to smoothout the experimental variations in the data, as for example, apparentvariations in hydrogen consumption.

Other work, including the desulfurization of thiophene, benzothiopheneand dibenzothiophene, has shown that the titania-zirconia-based catalystof this invention has an inherent hydrogenation capability, relative toits desulfurization activity, about twice that of the conventionalalumina based desulfurization catalyst. This entirely unexpectedproperly of the titania-zirconia based catalyst of this invention isextremely important in the long term processing of residua.

We do not wish to be bound by any theory, but the effect of reducinghydrogen consumption might be ascribed to a greater hydrogen-transfercapability of the catalyst. Such capability is important from thestandpoint of hydrogen transfer promotion in residua processing wherereactants and carrier hydrogen have limited access to the surface. Sincesuch capability would lead to a reduction in hydrogen consumption andsince the catalyst of this invention has led to reduced consumption, thestated theory is logical, even though it is speculation.

We claim:
 1. A catalyst composition, the catalyst support of whichconsists essentially of co-precipitated titania and zirconia, theco-precipitate having associated therewith a mixture of (1) cobaltmetal, cobalt oxide or cobalt sulfide and (2) molybdenum oxide ormolybdenum sulfide.
 2. The catalyst of claim 1 wherein thetitania-zirconia co-precipitate contains from about 20% to about 80% byweight of titania and from about 80% to about 20% by weight of zirconia.3. The catalyst of claim 1 wherein the two-component system consists ofcobaltia and molybdena.
 4. The catalyst of claim 3 wherein cobaltia andmolybdena are present in the range of from about 1% to about 10% andfrom about 2% to about 20%, respectively, both as a weight percent ofthe finished catalyst.
 5. The catalyst of claim 4 wherein cobaltia andmolybdena are present to the extent of 3% and 10% by weightrespectively.
 6. The catalyst of claim 1 wherein the ratio of ZrO₂ toTiO₂ is from about 0.5 to about 2.0:1.
 7. The catalyst of claim 6wherein titania and zirconia are present in the co-precipitate inequimolar amounts.
 8. The catalyst of claim 1 wherein the surface areaof the co-precipitate is from about 100 m² /g to about 250 m² /g.
 9. Acatalyst composition consisting essentially of a support of alumina,titania and zirconia having associated therewith a system selected fromthe group consisting of (a) Group VIB metal oxides or metal sulfides,(b) Group VIII metals, metal oxides or metal sulfides and (c) mixturesthereof.
 10. The catalyst of claim 9 having therein from about 15% toabout 45% by weight of titania, from about 25% to about 65% by weight ofzirconia and from about 10% to about 50% by weight of alumina, all as aweight percent of the carrier.
 11. The catalyst of claim 9 wherein thesaid system is a two-component system consisting of cobaltia andmolybdena.
 12. The catalyst of claim 11 wherein cobaltia and molybdenaare present in the range of from about 2% to about 10% and from about 5%to about 20%, respectively, both as a weight percent of the finishedcatalyst.
 13. The catalyst of claim 9 wherein the weight percent aluminain the alumina-zirconia-titania composite is from about 10 to about 50.14. A catalyst composition, the catalyst support of which consistsessentially of (A) co-precipitated titania and zirconia havingassociated therewith a mixture of (1) cobalt metal, cobalt oxide orcobalt sulfide and (2) molybdenum oxide or molybdenum sulfide or of (B)titania, zirconia and alumina having associated therewith a systemselected from the group consisting of (a) Group VIB metal oxides ormetal sulfides, (b) Group VIII metals, metal oxides or metal sulfidesand (c) mixtures thereof.